‘We do everything we can to control the numbers’
On Tuesday Victoria hit 1,763 cases. How did we get here? First, the Delta virus has now got its hooks well and truly into our population – we are not eliminating it from here. Once it gets into the casualised and essential workforce, multigenerational households, communities with English as a second language, lower socio-economic groups etc, it is very hard to stamp out.
Second, once it is in specific populations of our community, it is hard to predict what will happen next week and next month with case numbers.
Third, Melbourne now holds the world record for the longest time in lockdown, which comes with non-compliance.
This increase in numbers among the unvaccinated was always going to happen. The plan was to only let it happen once we were 80% (or more) double vaccinated. It has just happened two months earlier than the plan. Which means we are more vulnerable to explosive spread.
The goal at, say, 90%-plus vaccination was that nearly all older people (most vulnerable to Covid) would be vaccinated, and infections would be concentrated among younger unvaccinated folk with a scattering of milder infections among the vaccinated.
We are not quite there yet. But you can already see that in Victoria the number of people in hospital is less than what we saw in New South Wales. There, six weeks or so ago, the number of people in hospital was roughly a bit less than the daily cases. About 500 people are in hospital with Covid in Victoria at the moment. So less than in the NSW, even allowing for time lags. That is, we are starting to see a decoupling of hospitalisations and case numbers.
The red line we do not want to cross (or even get near) is 2,500 Victorians in hospital with Covid. That would see health services under immense strain, and quality of care for both Covid and other patients deteriorate. So, on this metric at least, we still have some headroom left.
What we need now is for the Victorian government to report daily the projected hospitalisation rate in 10 days to two weeks. It is not hard to do – just use the expected hospitalisation rates by age for cases and multiply them through the last few days of notifications to get a moving projection.
And if those hospitalisation rates look like they will crash through 2,500 people in hospital on any given day, we will need to hit the brakes: slow down the re-opening as per the road map and even – dare I say it – go back into hard lockdown. To be clear, I am not recommending this – just saying it is our last backstop.
And in the meantime, we do everything we can to control the numbers and protect our roadmap. We have recently published modelling of 100s of scenarios. It shows that we need at least 80% of children and adults vaccinated to have a moderately good life. Let’s get vaccination rates to 90% plus.
Moreover, we need to improve ventilation and air filtration in schools and other buildings; stockpile rapid antigen testing kits to use when we need them (eg for whatever workplace the infection is rife in three weeks, or at sporting events) and ask whoever develops the Covid-Safe app to get it working properly for Bluetooth enable contact tracing.
These innovations will give us more tools in the toolkit, so it is less likely we need to use lockdowns when things do go pear-shaped, as they will from time to time. And please keep doing the same old boring stuff – wear masks properly in higher-risk environments, physical distancing, and so on.
• Tony Blakely is a professor of epidemiology at the University of Melbourne
Vaccination means tolerating higher case numbers
Everyone is probably tired of hearing that vaccination is the key out of this pandemic. More than 82% of Victoria’s over-16 years old population have now had at least one dose, but this is already helping us to keep some control of infection rates and will be the key to us sticking with the road map.
Rising case numbers is not everyone’s idea of “control”, but there is a big difference between controlled growth and an out-of-control outbreak.
Victoria has struggled to get the reproduction number down in this latest outbreak, with this case growth measure pushing towards, or over, two on a few occasions causing our case numbers to more than double within a week. That kind of growth becomes more apparent, and more dangerous, as case numbers climb.
But Delta can have a reproduction number of six or more, so anything less than two makes an enormous difference. And, progressively, we have pushed that number down further, with it sitting at 1.1 just before the most recent hike in case numbers. Previously when we have seen a sudden jump in cases, it has taken a week or so for the reproduction number to settle again.
We are already at the vaccination rates New South Wales had when their case numbers plateaued, and that was the trend in the Victorian numbers too a week ago. Despite the setback, it’s important to know higher vaccination coverage can help quicken recovery from these sudden accelerations in cases.
Getting vaccinated not only reduces personal risk of infection and serious illness, but also the proportion of cases that end up in ICU. Burnet modelling predicts peak ICU demand to be about one to two weeks after the peak in case numbers, and about 18% of the number of new cases at their peak. We currently have 101 ICU admissions associated with a seven-day new case average of about 800 from 10 days ago: that’s 13%.
Faster vaccination uptake protects more people from serious illness and that then drives a wedge between case numbers and hospitalisations and allows us to tolerate higher case numbers, while still staying with the plan for easing restrictions.
It’s equally important that the average vaccination rates don’t disguise pockets in our community where low case numbers might let outbreaks spread faster and send a greater proportion of people with infections to hospital. The recently announced investments into those postcodes with lower vaccination rates is therefore very important. As vaccination rates lift in more vulnerable areas, the whole community is better protected, and new outbreaks are less likely to take hold.
Prevention is better than cure but equally we have seen the extraordinary lift in vaccination in some of the previous hotspots help turn cases numbers around dramatically. Hume, for example, saw vaccination rates rise nearly 20% in the adult population in a fortnight recently and case numbers are now less than a quarter of what they were.
Do we need more lockdown measures as well? I would say no. What matters most is that people resist the temptation to break the rules around the restrictions at the heart of lockdown rules for a few more weeks – not mixing across households indoors, or in other indoor settings without masks. We are now just weeks away from 70% fully vaccinated and holding the line on these core rules can help us to end lockdown with more manageable case numbers and less risk.
If relaxing some low-value rules, such as curfew and masks outdoors when away from others, helps people stay focused on the core rules, then this might be something else to consider over the next couple of weeks. But the most important thing we can do is to bring the finishing line forward with higher vaccination rates, reducing cases and hospitalisations in the process.
• Catherine Bennett is chair in epidemiology at Deakin University
